1. Field of the Invention
The present invention relates generally to running tools. More specifically, the invention relates to a running tool adapted to compensate for undesired torque in order to prevent premature release of a component secured to the running tool.
2. Background of the Invention
Running tools are used for various purposes during well drilling and completion operations. For example, a running tool is typically used to set a liner hanger in a well bore. The running tool is made up in the drill pipe or tubing string between the liner hanger and the drill pipe or tubing string running to the surface. In one aspect, the running tool serves as a link to transmit torque to the liner hanger to help place and secure the liner in the well bore. In addition, the tool also provides a conduit for fluids such as hydraulic fluids, cement and the like. Upon positioning of the liner hanger at a desired location in the well bore, the running tool is manipulated from the surface to effect release of the liner hanger from the running tool. The liner may then optionally be cemented into place in the well bore. In some cases, the cement is provided to the well bore before releasing the liner.
The application of torque to the drill string facilitates lowering the liner past obstructions formed in the well bore. For example, during drilling the drill bit often creates pockets in the surfaces of the well bore. While being lowered, the liner may move into the pockets. By rotating the liner, the liner is able to navigate through the pockets more easily.
In a typical drill pipe or tubing string, lengths of drill pipe or tubing are connected by tool joints using right-hand threads on the drill pipe. These joints are made up using right-hand torque and unscrewed or released using left-hand torque. Drilling is carried out by right-hand or clockwise rotation of the drill string to avoid breaking out or loosening the tool joints making up the pipe string. In the case of a mechanical release, left-hand torque is then applied o the drill string. In particular, the torque is sufficient to shear one or more shear screws located in the running tool. Subsequently, the liner may be detached from the running tool.
A problem occurs when the liner (or potentially even the running tool or drill string) engages an obstruction (e.g., a rock formation) that prevents continued clockwise rotation of the liner. As the surface actuator continues to provide torque to the drill string, the drill string is xe2x80x9cwound up,xe2x80x9d much like a rubber band or other elongated elastic member. Once the liner breaks free of the obstruction, the accumulated potential energy due to the winding up is converted into kinetic energy as the drill string unwinds by rotating in the clockwise direction. In some cases (where enough energy is available), the liner may over-travel the neutral drilling position. This has the effect of simulating a manual mechanical release because the running tool is now turning in a left-hand (counter-clockwise) direction relative to the liner. In the event the shear screws shear out, the running tool is prematurely released from the liner hanger.
Another problem with prior art methods and apparatus is balancing the need for sufficient strength of the shearing screws while still allowing them to shear out when necessary. Consider, for example, the case in which the liner hanger may be of relatively light weight. When the hanger is set and ready to be mechanically released, the applied left-hand torque may cause the hanger to rotate in tandem with the drill string, thereby inhibiting the release procedure.
Therefore, there exists a need for a running tool that compensates for over-travel of the tool to prevent prematurely releasing the tool from a liner hanger or other connected component.
The present invention is directed to a running tool for setting a liner or other tool down hole. The running tool generally comprises a torque-dampening system.
In one aspect, the invention provides a running tool for a well tool, comprising a first portion, a second portion and a torsion interface disposed therebetween. A torque-dampening system contacts the first portion and is adapted to inhibit the relative rotational movement between the first and second portions during an opposing linear displacement.
In another aspect, the invention a running tool comprising a torsion interface adapted to cause opposing linear displacement of a first and second portions upon their relative rotation. A tubular member is concentrically disposed within the first and second portions and the tubular member is slidably disposed relative to the first portion. A torque-dampening system is located between the tubular member and the first portion. When actuated in response to the opposing linear displacement of the first and second portions, the torque-dampening system inhibits the relative rotational movement between the first and second portions.
In another aspect, a mechanical release is provided to enable operation of a running tool without the assistance of hydraulic pressure and without conventional shearing screws, which are made to shear out during application of left-hand torque to the tool. The mechanical release assembly comprises a first sleeve and a second sleeve each carrying a plurality of intermeshed teeth (which do not necessarily contact one another). During application of left-hand torque, the teeth engage and ride up one another to linearly displace the first sleeve and a second sleeve. As a result, the first sleeve strokes up relative to a tubular member concentrically slidably disposed within the first sleeve. In response to the linear displacement of the sleeves, a torque-dampening system, located between a tubular member and the first sleeve, is actuated to inhibit the relative rotational movement between the sleeves. Upon a predetermined degree of rotation, the teeth disengage, rotate over one another and come to rest in a release position. Downward pressure is then applied to the tubular member, thereby shifting the tubular member down relative to the sleeves and causing the tool to disengage from a liner hanger coupled to a bottom portion of the tool.
In another aspect, a method for dampening rotation of a sleeve on a running tool is provided. The method comprises providing a first and second portion of a running tool, wherein a portion of the first portion is adapted to interface with a down hole tool. The rotation of the first portion is then restricted by actuating a fluid-actuated torque-dampening system operably connected to the first portion. In one embodiment, the first portion is operably connected to a second portion. The movement of the first portion is then restricted such that movement of the second portion is also restricted.